Method for magnetooptic current measurement and magnetooptic current-measuring device

Abstract

Simple methods for magnetooptic current measurement and magnetooptic current-measuring devices are specified, which are independent of temperature influences on the measurement result and require no compensation device for the light intensity of light sources (LD1, LD2) employed. Light beams (1, 2) from the two laser light sources (LD1, LD2) are alternately polarized orthogonally relative to one another by means of a beam splitter (3), and are transmitted to light detectors (D A , D B ) via collimators (4, 6), which are connected via a polarization-maintaining high-index birefringent HI fiber (5), through a magnetooptic current sensor (7), an analyzer (10), 2 collimators (11, 12) and multimode fibers (13) and (14). 1st and 2nd light output signals S A1 and S B1 as well as 3rd and 4th light output signals S A2 and S B2 are derived sequentially in time from the light detectors (D A , D B ). A signal characterizer (232) of a control and evaluation device (15) is used to calculate a current intensity I detected by means of the magnetooptic current sensor (7), in accordance with I= S A1 ·S B2 /(S A2 ·S B1 )-1!/(8·V), V being the magnetooptic Verdet's constant. It is also possible to work using frequency multiplexing instead of time multiplexing. It is possible to use a low-index birefringent LI fiber instead of a solid optical current sensor (7), light being sent through in both directions and evaluated separately.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 
     
       1. A method for magnetooptic current measurement, wherein a) first and second input light beams are guided in first and second directions of polarization, oriented at right angles to one another,   b) through a magnetooptic current sensor and   c) subsequently through an analyzer by means of third and fourth directions (A, B) of polarization, oriented at a prescribable angle relative to one another,   d) from which analyzer at least first and second output light beams in the third and fourth directions (A, B) of polarization are transmitted to at least first and second light detectors at which, on the output side, at least first and second output signals (S A , S B  ; S A1 , S A2 , S B1 , S B2 ) which are proportional to the received light intensity can be tapped,   e) the third and fourth directions (A, B) of polarization of the analyzer being rotated by a prescribable angle relative to the first and second directions of polarization of the input light beams into the magnetooptic current sensor, and   f) said first and second output signals being derived from said first input light beam via the output side of the first and second light detectors, and   g) third and fourth output signals being derived from said second input light beam via the output side of the first and second light detectors, wherein   h) current intensity I detected by the magnetooptic current sensor is output proportional to at least one of:   I={arc sin  (Q.sup.0.5 -1)/(Q.sup.0.5 +1)!}/(2·V)i)(1)     or at least approximately proportional thereto: and     I=(Q-1)/(8·V)                                     (2)     where     Q=S.sub.A1 ·S.sub.B2 /(S.sub.A2 ·S.sub.B1),     and V signifies a magnetooptic Verdet's constant.     
     
     
       2. Method for magnetooptic current measurement, wherein a) first and second input light beams are guided in first and second directions of polarization, oriented at a prescribable angle relative to one another,   b) through a magnetooptic current sensor and   c) subsequently through an analyzer via third and fourth directions (A, B) of polarization, oriented at a prescribable angle relative to one another,   d) from which analyzer at least first and second output light beams in the third and fourth directions (A, B) of polarization are transmitted to at least first and second light detectors at which, on the output side, at least first and second output signals (S BA1 , S BB1  ; S BA2 , S BB2 ) which are proportional to the received light intensity can be tapped,   e) the third and fourth directions (A, B) of polarization of the analyzer being rotated by a prescribable angle relative to the first and second directions of polarization of the input light beams into the magnetooptic current sensor, and   f) said first and second output signals being derived from said first input light beam via the output side of the first and second light detectors, and   g) third and fourth output signals being derived from said second input light beam via the output side of the first and second light detectors, wherein   h) the magnetooptic current sensor is an optical fiber,   i) at least two of said first and second input light beams and third and fourth input light beams being additionally guided in an opposite direction by said optical fiber,   j) fifth and sixth output signals being derived from at least one of the first and third input light beams via the output of third and fourth light detectors and   k) seventh and eighth output signals being derived from at least one of the second and fourth input light beams via the output of the third and fourth light detectors, and   l) current intensity I detected by the magnetooptic current sensor is output proportional to:   I={arc sin  (QH.sup.0.5 -1)/(QH.sup.0.5 +1)!+arc sin  (QR.sup.0.5 -1/(QR.sup.0.5 +1!}/(4·V)     wherein     QH=S.sub.BA1 ·S.sub.BB2 /(S.sub.BA2 ·S.sub.BB1),       QR=S.sub.AA1 ·S.sub.AB2 /(S.sub.AA2 ·S.sub.AB1),     and   V signifies a magnetooptic Verdet's constant.     
     
     
       3. The method as claimed in claim 1, wherein the input light beams have the same wavelength. 
     
     
       4. The method of claim 1, wherein differently polarized first and second or third and fourth input light beams are carried alternatingly, in chronological succession, through the magnetooptic current sensor.   
     
     
       5. The method of claim 1, wherein a) differently polarized first and second input light beams are modulated in their intensity with two different frequencies and   b) the output signals of the light detectors are each subjected to bandpass filtration with these two frequencies in order to obtain the output signals of the light detectors which are proportional to optical power.   
     
     
       6. The method as claimed in claim 2, wherein the input light beams have the same wavelength. 
     
     
       7. The method as claimed in claim 2, wherein differently polarized first and second or third and fourth input light beams are carried alternatingly, in chronological succession, through the magnetooptic current sensor.   
     
     
       8. The method of claim 2, wherein a) differently polarized first and second input light beams are modulated in their intensity with two different frequencies, and   b) the output signals of the light detectors are each subjected to bandpass filtration with these two frequencies in order to obtain the output signals of the light detectors which are proportional to optical power.